Heat exchanger



June 6, 1944. WORN 2,350,976

HEAT EXCHANGER Filed Jan. 16, 1945 11 10 18 /L V w 21.

l i J INVENTOR BY x 42w ATTORNEY Patented June 6, 1944 UNITED STATES mOFFICE @3133... George A. Worn, Greenwich, Conn. Application January 16,194:, sci-a1 No. 472,571 1 Claims. (01. 251-202) This invention relatesto heat exchangers and particularly to improvements in heat-exchangertubing of the type provided with an extended heat-conducting surface inthe form of external fins extending along the tubingto increase the heatconduction between ajfluicl within the tubing and a fluid surroundingthe tubing.

Heretofdre, the employment of such flns upon tubes arranged in a groupor bundle has presented a serious difficulty in the way of cleaning thetube, surfaces and the fin surfaces located within the bundle.Generally, the fluid circulating around the tubes leaves upon thesurfaces of the tubes and the flnsa deposit which materially impairstheir heat transfer elflciency and which it is highly desirable toremove. jrhe fins, however, obstruct-lateral insertion of a scrapin toolinto-the tube bundle for removal of such deposit so that it is possible,if, at all, to scrape the tube surfaces and the extended surfaceslocated within thebundle only by insertion of a tool into one end of thebundle and operation of such tool lengthwise of the tubing. Even in suchcase, however,'the tubing isoften quite long, and the intertube andinterfln spaces are quite narrow so that a very long, slender tool isrequired to reach the entire...area of-the'surfaces to be cleaned. Itisdlfllcult and sometimes impossible to remove the deposit in such amanner particularly where the tubing is relatively long.

An important object of my present invention is to provide improvedflnned heat-exchanger tublug-designed to facilitate cleaning of thesurfaces thereof located within a tube group or bundle.

Another important object of my invention is to provide, in aheat-exchanger tubebundle, an improved arrangement of tubes andheat-conducting flns in a correlation such as to provide suflicientclearances around and within the bundle for convenient insertion of ascraping tool transversely or laterally of the bundle and for eflicientoperation of the tool to clean all of the tube surfaces and the extendedsurfaces exposed within the bundle.

A further object of my invention is to provide finned tubing having theaforesaid advantages and devised particularly for satisfactoryembodiment in a heat exchanger such as that disclosed in the copendingapplication of George A. Worn and Edward A. Bertram, Serial No. 453.234,flied August 1', 1942. I

Other objects and advantages of my invention will appear hereinafter.

In the drawing.

Fig. l is a vertical longitudinal sectional view of a'heat exchangerembodying my invention;

Fig. 2 is a horizontal longitudinal sectional view of the heat exchangershown in Fig. 1;

Fig. 3 is an enlarged transverse section taken along the line 3-8 ofFig. 1;

Fig. 4 is a further enlarged transverse section of the inner tubing unitor bundle removed from the outer tube or shell of the heat exchangerwherein the manner of laterally inserting the scraping tool into theinterior of the unit is indicated; and

Fig. 5 is a view similar to Fig. 4 and illustrates is modifiedarrangement of the fins upon the tub- My invention is illustrated anddescribed as embodied in a heat exchanger such as that disclosed in theaforesaid copending application, although it is not necessarily limitedthereto. This invention was particularly devised to provide forconvenient and thorough cleaning of the heat-conducting surfaces of sucha heat exchanger.

In general, the heat exchanger unit disclosed in such copendingapplication is one of a doublepipe type. This unit comprises anelongated outer tube ill of welded construction formed in three sectionsincluding a long main tube section ll, a cover I! welded, as at It, toone end of said main section, and an annular flange section It welded asat" to the opposite end of the main section. The flange section isformed with a thick peripheral flange l8 and a tapering tubular neck ll.The bore of the flange section is flared at its outer end, as at l8, andthe section is formed with a relieved face around the mouth of the boreand with "a gasket-receiving groove 20 in the face. A thick cover plateor disk 2| has a similar face and a similar groove 22 in opposition tothe groove 20. A metal gasket rin 23 of a depth exceeding the combineddepth of the grooves has its edges seated in the grooves. The grooveshave flat bottoms and inwardly 'converging side walls; and the edges ofthe gasket are beveled to wedge in the grooves. Bolts 24 extend throughholes in flange l6 and the cover plate 2| and have nuts 25 screwed upontheir opposite ends to secure the plate to the flange and to hold thegasket under compression.

Cover plate 2! has a fluid inlet passage 28 and a fluid outlet passage21 extending between its faces. Through most of the thickness of theplate, these passages are parallel; but, adjacent the inner face of theplate, they converge and open through flat abutments 20 at the bottom offlared counterbores 28 at the inner face of the plate. These abutmentsare at right angles to the converging ends of the passages. At the outerface of the plate, the passages are counterbored to provide them with aflared or beveled seat 30.

Within the outer tube "I there is an inner tube unit forming a smalltube bundle defined by a single bifurcated U-tube. Tubular stems II and82, at the forward end of the outer tube, form the end portions of thisU-tube. Stem 3| is the inlet stem and opens into a tubular fork fins, atleast all the fins on each tube, have the same radial dimension.

In the arrangement of the fins shown in Figs. 1 to 4, inclusive, eachtube 34 is provided with only two of the fins 42 within asemiclrcumference of the tube. One of these fins projects into the spaceII. From this fork, parallel branched tubing 34 extends forwardly forthe major portion of the length of the outer tube, forms return bends35, and, from these bends, extends in a reverse direction to a tubularfork 36 opposite the first fork and connected to the outlet stem 32. Inthe present instance, there are two of the branch tubes in each leg ofthe U-tube, and they provide for divided flow from the stem 3! to thestem I2. Their caliber is desirably smaller than that of the stems. Attheir outer ends, the stems SI and 32 are secured and sealed incommunication with the passages 28 and 21, respectively,

- in the cover plate. The outer end portions of 'the stems diverge inorder to reach the passages, 'and the ends of the stems contact squarelywith structed in the manner described in the above,

copending application.

Inlet and outlet connections such as those disclosed in the aforesaidcopending application, for example, may be sealed to the cover plate 2|in communication with the passages 26 and 21, respectively, to providefor circulation of a fluid through the inner tubing. The outer tube isprovided, at points near its opposite ends, with an inlet nipple l0 andoutlet nipple 4| to provide for circulation of another fluid through theouter;

tube and around the inner tubing.

The four parallel longitudinal sections of the tubing 34 are desirablyprovided with radially projecting heat-conducting fins 42 extendingalong most of the length of the sections. In order to. accommodate theimproved fin arrangement of my invention, these four tube sections,which, in effect, form a bundle of four tubes, are preferably equallyspaced around a central space within the bundle and substantiallyentirely around such space and are desirably located equidistantly fromthe central longitudinal axis of the bundle. In the present instance,the tubes are spaced apart aroimd said space a distance approximatelyequal to the outside diameter of the tubes. Each fln de-i sirably has anapproximately triangular crosssectional shape and is desirably formed ofa strip oi sheet metal bent along longitudinal lines into a triangularform with its opposite longitudinal edges meeting at the apex of thetriangle and!" there welded together. The portion of the fin forming thebase of the triangle is made concave to fit the tubing and is weldedthereto so that the fin projects radially from each tube. For thepurposes of my invention, it is desirable that all the lo surrounded bythe tubes, and the other fin projects away from said space. The inwardlyprojecting fins oi' the four tubes are arranged ap proximatelytangentially to an imaginary circle concentrically positioned withrespect to the tube bundle and having a diameter approximately equal tothat of the tubes. These fins also terminate at such circle. Therefore,the crests or inner edges of the successive fins are spaced ninetydegrees apart armmd the circle to provide liberal clearance between thefins. The outwardly projecting fins are preferably arranged anproportioned so that their crests or outer edges lie approximately uponan imaginary circle surrounding the tube bundle and approximatelytangential to the peripheries of the four tubes 34.

The arrangement of the fins just described provides clearances aroundand within the tube bundle so as to enable a straight scraping tool T tobe inserted transversely oi the bundle and operated conveniently atvarious angles, as indicated in Fig. 4, to clean all of the surfaces ofthe tubes and the fins upon which any deposit accumulates. At the sametime, this arrangement provides a good distribution of the fins withinthe outer tube II for efficient heat exchange between the fluid wthinthe inner tubing and the fluid within the outer tube. I

In the form of my invention shown in- Fig. 5, the arrangement of thetubes 34 is identical with that just described, but each tube isprovided with three fins 4211. One of these fins upon each tube projectsradially of the latter straight toward the center of the bundle, and theinwardly projecting fins of all the tubes have their crests or inneredges arranged approximately equidistantly from the center of the tubebundle and terminating radially upon an imaginary circle centrallylocated with respect to the tubes as indicated. The other two fins ofeach tube are desirably arranged at least ninety degrees outwardlyaround the tube from the inwardly projecting fin and project radially inopposite directions from the tube. These outer fins are arranged anproportioned to provide liberal clearance for insertion of the scrapingtool between the crests of the fins upon adjacent tubes and forconvenient operation of the tool to clean all of the exposed tube andfin surfaces within the tube bundle. This modifled arrangement of thefins provides additional extended surface and also provides a gooddistribution of the fins in the bundle for efi'ective heat conduction.

Although I have shown a four-tube arrange- 0 ment, my invention issusceptible of embodiment in a tube bundle having a different number oftubes. In addition, my invention is not necessarily limited to the useor the triangular type of fin shown. while I have disclosed a preferredform of embodiment of my' invention, it will be understood that it ispossible to modify details of the structure disclosed without departingfrom the invention as defined in the appended claims.

I claim:

1. A heat-exchanger tube bundle comprising a group of four paralleltubes of approximately the same diameter spaced apart a distanceapproximately equal to said diameter around a central space andapproximately equidistantly from the center of said space, a pair ofexternal radial heat-conducting fins borne by each of said tubes andextending longitudinally thereof. one of said fins upon each tubeprojecting into said space, all of said inwardly projecting finsterminating upon and being tangential to a circle centrally locatedwithin the said space and having approximately the same diameter as thetubes, the other fin upon each tube diverging outwardly from theinwardly projecting fin relatively widely but at an angle thereto lessthan 180 and being materially spaced from the next adjacent tube, tothereby provide intertube and interfin clearances around and within thebundle for straight insertion of a scraping tool transversely of thebundle and into contact with all of the exposed tube surfaces and thefin surfaces and for operation of the inserted tool for completescraping of said surfaces.

2. A'heat-exchanger tube bundle comprising a group of parallel tubesspaced apart around a central space and approximately equidistantly fromthe center of said space, three external radial heat-conducting finsborne by each of said tubes and extending longitudinally thereof, one ofsaid fins upon each tube projecting into said space, all of saidinwardly projecting fins terminating upon and being radial to a circlecentrally located within said space, the other two fins of each tubediverging outwardly from the inwardly projecting fin relatively widelybut at an angle thereto of less than 180 and being spaced materiallyfrom the fins of adjacent tubes of the group, to thereby provideintertube and interfin clearances around and within the bundle forstraight insertion of a scraping tool transversely of the bundle andinto contact with all of the exposed tube surfaces and the fin surfacesand for operation of the inserted tool for complete scraping of saidsurfaces.

3. The heat-exchanger tube bundle as claimed in claim 2, wherein each ofthe outwardly extending fins on each tube is spaced at least ninetydegrees around the tube from the inwardly projecting fin, one on eachside of the latter, andall of said fins have substantially the sameradial dimension.

4. A heat-exchanger tube bundle comprising a group of four paralleltubes of approximately the same diameter spaced apart a distanceapproximately equal to said diameter around a central space andapproximately equidlstantly from the center of said space, a pair ofexternal radial heat-conducting fins borne by ach of said tubes andextending longitudinally thereof, one of said fins upon each tubeprojecting into said space, all of said inwardly projecting finsterminating upon and being tangential to a circle centrally locatedwithin the said space and having approximately the same diameter as thetubes, the other fin upon each tube diverging outwardly, with respect tosaid space, from the inwardly projectbundle and into contact with all ofthe exposed tube surfaces and the fin surfaces for complete scraping ofsaid surfaces.

5. In a heat-exchanger tube bundle comprising a circular series ofparallel tubes spaced around a central space within the bundle,heatconducting fins including a pair of external radial fins borne byeach of said tubes and extending longitudinally thereof and divergingfrom each other relatively widely but at an angle of less than 180 andin a direction toward the next succeeding tube around the series, one ofsaid fins of each pair projecting into said space, the crests of saidfins upon each tube lying upon a plane intermediate the tube and thenext succeeding tube and the said fins upon the latter tube beingcircumferentially positioned thereon to space their crests from saidplane, to provide intertube and interfin clearances around and withinthe bundle for straight insertion of a scraping tool transversely of thebundle and into contact with all of the tube surfaces and the finsurfaces exposed within the bundle and for operation of the insertedtool for complete scraping of said surfaces.

6. In a heat-exchanger tube bundle comprising a group of parallel tubesspaced around a central space within the bundle, heat-conducting finsincluding a pair of external fins borne by each of said tubes andextending longitudinally thereof and diverging outwardly from each otherrelatively widely but at an angle of less than 180, one of said finsprojecting inwardly into said space and the other fin projectingoutwardly of said space and the pairs of fins of the successive tubesaround said space being in positions progressively displacedcircumferentially of the tubes, to provide intertube and interfinclearances around and within the bundle for straight insertion of ascraping tool transversely of the bundle and into contact with all ofthe tub surfaces and the fin surfaces exposed within the bundle and foroperation of the inserted tool for complete scraping of said surfaces.

7. In a heat-exchanger tube bundle comprising a group of parallel tubesspaced around a central space within the bundle, heat-conducting finsincluding a pair of external fins borne by each of said tubes andextending longitudinally thereof and diverging outwardly from each otherrelatively widely but at an angle of less than 180', each of said finsbeing approximately triangular in cross-section and tapering outwardlyfrom its respective tube, one of said fins projecting inwardly into saidspace and the other fin projecting outwardly of said space and the pairsof fins of the successive tubes around said space being in positionsprogressively displaced circumferentially of the tubes to provideintertube and interfin clearances around and within the bundle sertedtool for complete scraping of said surfaces.

onoaon A. WORN.

